5,11-diloweralkylindolo[3,2-b]carbazole-6,12(5h,11h)-dione



1 .molecular cyclization dependent United States Patent .carbazole-6,l2(5H,11H)-diones and to a novel process for preparing the same from l-alkyl-Z-indolecarbonyl halides.

The 5,11-dialkylindolo[3,2-b]carbazole-6,l2(5H,llH)- diones of the present invention have the formula:

' forms thereof.

' The starting materials for preparing the compounds of Formula I are l-alkyl-Z-indolecarbonyl halides having the formula:

7 wherein R is as given above and X represents halogen having an atomic number from 17 to 35, i.e., X is chloline or bromine, preferably chlorine.

The compounds of Formula I are prepared by the interof two molecular equivalents of 1- alkyl-Z-indolecarbonyl halide of Formula II to produce two molecular equivalents of hydrogen halide and one molecular equivalent of the desired 5,1l-dia1kylindolo- [3,2-b]carbaZole-6,12(5H,11H)-dione. The reaction is carried out by mixing a l-alkyl-2-indolecarbonyl halide and a Friedel-Crafts catalyst in the presence of an inert solvent while maintaining the mixture at a suitable re action temperature until the desired reaction has occurred. Examples of inert solvents are ethylene dichloride, 1,1,2, 2-tetrachloroethane, carbon disulfide, nitrobenzene, and the like. Examples of Friedel-Crafts catalysts are aluminum chloride, aluminum bromide, boron trifluoride, and the like, aluminum chloride being preferred. The molar ratio of 1-alkyl-2-indolecarbonyl halide to catalyst, although not highly critical, advantageously ranges from about 1:1 to about 1:4, and preferably ranges from about 1:1.5 to about 112.5. The reaction can be carried out at temperatures ranging from about C. to about 35 C., or even somewhat higher or lower. Preferably the reaction is carried out between about 15? C. and about 30 C. The time required for completing the reaction is on various factors, such as the reaction temperature, the particular Friedel-Crafts catalyst and/ or 1- alkyl-2-indolecarbonyl halide, etc. In general, however, the time required for completing the reaction seldom exceeds about 6 hours,'and frequently is much less, such as 7 about 0.5 hour. Upon completion of the reaction, the

5,11 1 dialkylindolo[3,2-b]carbazole 6,12(H,l1H) dione product can be isolated and purified by conventional means, such as by adding 1765, 1946; Audrieth et al., J. Org.

, ing humans.

. phenylhydrazine of the 2 aqueous acid (e.g., hydrochloric acid) to the reaction mixture, recovering the product by filtration, and recrystallizing it.

The starting 1-alkyl-2-indolecarbonyl halides of For mula II are prepared from the corresponding l-alkyl-Z- L indolecarboxylic acids having the formula:

wherein R is as given above,

using procedures commonly employedfor converting carboxylicacids to acid halides, e.g., by treatment of an acid of Formula 111 with a phosphorus chloride or bromide. The procedure of Johnson et al., J. Am. Chem. Soc. 67, 423, 1945, which involves the use of phosphorus pentachloride in an ethereal medium is particularly satisfactory.

The l-alkyl-Z-indolecarboxylic acids of Formula III can be prepared by known procedures, e.g., by the procedure of Snyder et al., J. Am. Chem. Soc. 78, 969, 1956, which involves reacting pyruvic acid with a l-alkyl-lformula c H5'-NR-NH2, wherein R is as given above, to obtain the hydrazone, and cyclizing the latter in the presence of an acid medium.

The 1-alkyl-l-phenylhydrazines are well known and can be prepared in various ways. See Fischer,.Ann. 190, 152, 1878', FierZ-David et al., Helv. Chiin. Acta 29, Chem. 6, 417, 1941.

The .novel 5,11 dialkylindolo[3,2-b]carbazole 6,12- (5H,llH)-diones of the invention have central nervous system depressant activity, and can be used for effecting sedation and tranquilization in birds and animals, includ- In addition, zole-6,l2(5I-l,1lH)-diones of the present invention exhibit high absorption of 280-300 millimicrons and accordingly can be employed as effective sun screens when incorporated in suitable vehicles such as transparent film-forming compositions and oils. 7

The following examples are illustrative of the process and products of the present invention but are not to be construed as limiting.

EXAMPLE 1 5,1I-Dimethylindolo[3,2-b1Carbdzole- 6,12(5H,11H)Dione Aluminum chloride (4.0 g.; 0.03 mole) was added during 5 min. toa stirred solution of 1-methyl-2-indolecar bonyl chloride (2.9 g.; 0.015 mole) in 20 ml. of ethylene dichloride. The resulting dark solution was stirred at about 25 C. for 30 min. Ice (10.0 g.) was added, fol-r lowed by dilute'hydrochloric acid (6 m1. of concentrated hydrochloric acid and 32 ml. of water). The mixture was stirred for 1 hr., and the filter cake was washed with water and dried. There was thus obtained 1.0 g. (42 percent yield) of 5,1l-dimethylindolo[3,2-b]carbazole-6, 12(5H,11H)-dione as a redsolid having amelting point of 365 C. Recrystallization from dimethylformamide afforded red needles having the same melting point.

Analysis.-Calcd. for C H N O C, 76.42; H, 4.49; N, 8.91. Found: C, 76.45; H, 5.17; N, 9.20. The ultraviolet absorption spectrum of the compound (in dimethylformamide-ethanol) exhibited maxima at s'h 268, 279, 295, 346, and 403 millimicrons.

The infrared absorption spectrum of the compound (mineral oil mull) showed: =CI-I 3040; C O'1640, C=C 1615, 1575, 1545, 1502, and 1495 cmf a 6 Patented May 26, 1964 the novel 5,1l-dialkylindolo[3,2-b]carbaof radiation in the wavelength range.

EXAMPLE 2 5,1l-Diethylindolo[3,2-12] Carbazole- 6,12 (5H,]1H) -Dine Following the procedure of Example 1, but substituting 1-ethyl-2-indolecarbonyl chloride for l-methyl-Z-indolecarbonyl chloride, there Was obtained 5,11-diethylindolo- 3,2-b] carbazole-6, 1 2 H, 1 1H) -dione.

EXAMPLE 3 5 ,1 I -Diis0propylind0l0 [3,2-b] Carbazole- 6,12(5H,11H)-Dione Following the procedure of Example 1, but substittuing 1-isopropyl-2-indolecarbonyl chloride for l-methyl-Z-indolecarbonyl chloride, there was obtained 5,11-diisopropylindolo[3,2-b]carbazole-6,l2(5H,11H)-dione.

EXAMPLE 4 5,11-Di-Sec.Butylindolo[3,2-b]Carbazole- 6,12(5H,11H) -Dl'0ne Following the procedure of Example 1, but substituting 1-sec.butyl-2-indolecarbonyl chloride for l-methyl-Z-indolecarbonyl chloride, there was obtained 5,11-di-sec. butylindolo[3,2-b]carbazole-6,12(5H,1lH)-dione.

EXAMPLE 5 sisting of 5,11-dimethylindolo [3,2-b]carbazole-6,l2(5H, 11H)-di0ne, 5,11-diethlindolo[3,2-b]carbazole-6,12(5H, 11H) -dione, and S-ethyl-l l-rnethylindolo [3,2-b] carbazole-6,12 (5H,11H)-dione. This mixture can be separated into the individual components by means of fractional crystallization from dimethylformarnide.

4 I claim: 1. A compound of the formula:

wherein R is alkyl of 1 to 4 carbon atoms, inclusive.

2. 5,11 dimethylindolo[3,2-b]carbazole 6,12(5H, 11H)-dione. I

3. A process for preparing a compound of the formula:

wherein R. is alkyl, which comprises mixing a Friedel- Crafts catalyst and an acid halide of the formula:

N 0 references cited. 

1. A COMPOUND OF THE FORMULA: 